Antimicrobial compositions comprising single domain antibodies and pseudomonas exotoxin

ABSTRACT

The present invention provides heavy chain immunoglobulins of the VHH type or fragment thereof having affinity for a target antigen of interest, including glycoprotein D2 (gD2) of HSV-2 or antigen thereof, and for envelope proteins of HIV-1 or an antigen thereof linked to  Pseudomonas  exotoxin A or functional fragments thereof. Also included are multimeric forms of the immunoglobulins and their use in the prevention and/or treatment of HSV2 and/or HIV-1.

REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/922,927, filed on Jan. 2, 2014, which is herebyincorporated by reference for all purposes as if fully set forth herein.

STATEMENT OF GOVERNMENTAL INTEREST

This invention was made with government support under grant no.R21AI079794 awarded by the NIH. The government has certain rights in theinvention.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ELECTRONICALLY

The instant application contains a Sequence Listing which has beensubmitted in ASCII format via EFS-Web and is hereby incorporated byreference in its entirety. Said ASCII copy, created on Dec. 31, 2014, isnamed P12627-02_ST25.txt and is 24,294 bytes in size.

BACKGROUND OF THE INVENTION

The variable domain of heavy-chain only antibodies found in members ofthe camelid family represents the smallest naturally occurringfunctional domain of the antibody molecule. These variable domains,termed VHH, have the same antigen binding capability as full-lengthantibodies, yet are typically around 15 kDa in size. When cloned andpurified as monomeric domains, VHH demonstrate remarkable stabilityunder a wide range of denaturing, temperature, and pH conditions. VHHsexhibit increased solubility compared to full-length antibodies or otherantibody fragments, and very high expression levels have been achievedin E. coli, yeast, and tobacco expression systems. Due to a high degreeof sequence homology between camelid and other mammalian variabledomains, VHH have been shown not to be immunogenic in mice. As a resultof their small size, VHH have enhanced tissue penetration, and anextended CDR3 loop allows VHH access to cryptic epitopes inenzymatically active sites that are unavailable for binding by fulllength antibodies.

Given their unique combination of characteristics, VHH have beenpromoted as promising biomedical tools. A myriad of VHH have beensuccessfully developed for diverse purposes including diagnostics,imaging, and biochemical and therapeutic applications. In terms of thediversity of pathogens that have been targeted thus far, VHH directedagainst viruses, bacteria, protozoa, and fungi have all been identified.VHH can act as a monomeric domain, or they can be expressed in amultivalent context to increase avidity and activity. Additionally,bispecific VHH can be assembled that bind different epitopes, which canin some cases dramatically increasing neutralization efficacy.

HSV-2 is one of the most prevalent sexually transmitted infections(STIs) in the world, and recent estimates indicate that roughly 16% ofpeople ages 15-49 worldwide are infected. There has been great interestin the development of a prophylactic vaccine to prevent HSV-2 infectionover the past several decades, but unfortunately, an effective one hasyet to be developed.

Human immunodeficiency virus type I (HIV-1) is also a sexuallytransmitted infection, and has contributed to an estimated 40 milliondeaths since it was first recognized in 1981. Currently, over 30 millionpeople worldwide are living with the virus. The development of effectiveHIV-1 vaccine immunogens that can elicit high titer, potent, and broadlyneutralizing antibodies (bnAbs) remains a major challenge.

Entry of HIV-1 into target cells is mediated by binding of highlyconserved epitopes on HIV envelope glycoproteins (Env) to a primarycell-surface receptor CD4. Binding of Env to CD4 initiates a series ofconformational changes of the Env structure, leading to exposure and/orformation of coreceptor binding sites that are recognized by cellsurface co-receptors (e.g. chemokine receptors CCRS or CXCR4). SinceHIV-1 was first discovered more than two decades ago, conventionalvaccine strategies have failed to develop effective vaccine candidatesthat can elicit potent broadly cross-reactive HIV-1-neutralizingantibodies. There continues to be a pressing need for novel HIV vaccinestrategies and compositions that can control the spread of HIV/AIDSpandemic.

A microbicide is a substance that can be applied to mucosal surfaces,including the vagina and rectum, to prevent infection with an STI. Asignificant public health goal has been to try develop a successfulmicrobicide against HSV-2 and HIV-1, including vaginal delivery ofantiviral drugs, antibody-based strategies, and small-interfering RNAs.It has been demonstrated that vaginally applied monoclonal antibodiesand single chain antibody variable fragments (scFv) directed against gD2protect against HSV-2 infection in animal models. The issue of how tovaginally deliver a neutralizing antibody against HSV2 or HIV-1 withoutthe direct application of the antibody immediately prior to sexualintercourse has yet to be resolved, however. Furthermore, the currentmethods of production of monoclonal antibodies and scFvs can becost-prohibitive to scale up, as antibodies are complex molecules withmultiple protein chains that are not easily purified and assembled.

As a result, there still exists an unmet need for alternative strategiesto prevent transmission, including the development of an effectivemicrobicide using means other than scFvs.

SUMMARY OF THE INVENTION

The isolation of an antibody fragment that neutralizes HSV-2 or HIV-1,and is structurally simple enough to be produced by the native bacterialflora of the vagina would solve both the production and deliverychallenges of the antibody-based microbicide strategy. Members of theCamelid family (camels, alpacas, and llamas), naturally produceantibodies that are devoid of light chains, so that the antigen bindingregion is solely contained in the variable region of the heavy chain,referred to as VHH (FIG. 1). These VHH domains retain the potent bindingcapacity of full-length antibodies, are stable under a wide range oftemperature and pH conditions, and are not immunogenic. Anotherattractive characteristic of VHH antibodies is that they are smallenough to be secreted by many types of commensal bacteria, including,for example, Lactobacilli, an ideal organism for delivery of VHHantibodies because they are a major component of the vaginal flora andbecause systems for expression of heterologous proteins have beendeveloped for these bacteria.

Using a VHH antibody that bound to gD2 of HSV-2, in an embodiment, theinventors created a P. aeruginosa Exotoxin A (PE)-based immunotoxin thatspecifically targets HSV-2 infected cells. This immunotoxin specificallybinds to cells expressing gD2 at the cell surface, causinginternalization of the entire protein, allowing the exotoxin A portionto act by halting protein synthesis, ultimately resulting in cell death.

In accordance with an embodiment, the present invention provides a heavychain immunoglobulin of the VHH type or fragment thereof having an aminoacid sequence of at least 85% identity to SEQ ID NO: 3 (R33) and havingaffinity for glycoprotein D2 (gD2) of HSV-2 or antigen thereof.

In accordance with another embodiment, the present invention provides aheavy chain immunoglobulin of the VHH type or fragment thereof having anamino acid sequence of at least 85% identity to SEQ ID NO: 4 (R33) andhaving affinity for glycoprotein D2 (gD2) of HSV-2 or antigen thereofthat is covalently linked to the P. aeruginosa Exotoxin A subunit or afunctional portion or fragment thereof.

In accordance with a further embodiment, the present invention providesa multimeric molecule comprising a heavy chain immunoglobulin fragmentof the VHH type as described herein, in which VHH sequences are fused toyield multimeric units of 2 or more VHH units optionally linked via aspacer molecule.

In accordance with still another embodiment, the present inventionprovides a multimeric molecule comprising two or more VHH sequences asdescribed herein, which are fused to yield 2, 3, 4 or 5 or more VHHunits optionally linked via a spacer molecule.

In accordance with an embodiment, the present invention provides anucleic acid encoding a heavy chain immunoglobulin fragment of the VHHtype as described herein.

In accordance with another embodiment, the present invention provides anexpression vector comprising the gene encoding the heavy chainimmunoglobulin fragment described herein.

In accordance with still another embodiment, the present inventionprovides a micro-organism transformed with the expression vectordescribed herein.

In accordance with a further embodiment, the present invention providesa method for the therapy or prophylaxis of HSV2 infection, comprisingadministering to a patient a heavy chain immunoglobulin or fragmentthereof described herein or the multimeric molecule described herein.

In accordance with another embodiment, the present invention provides amethod for the therapy or prophylaxis of HSV2 infection, comprisingadministering to a patient a micro-organism described herein expressingthe heavy chain immunoglobulin or fragment thereof described herein, orthe multimeric molecule described herein. In some embodiments themultimeric molecule comprises the amino acid sequence of SEQ ID NO: 4.

In accordance with another embodiment, the present invention provides aheavy chain immunoglobulin of the VHH type or fragment thereofcomprising an amino acid sequence of at least 85% identity to SEQ IDNOS. 7 or 11, and having affinity for envelope proteins of HIV-1.

In accordance with yet another embodiment, the present inventionprovides a heavy chain immunoglobulin of the VHH type or fragmentthereof comprising an amino acid sequence of at least 85% identity toSEQ ID NOS. 8 or 12, and having affinity for envelope proteins of HIV-1which is covalently linked to the P. aeruginosa Exotoxin A subunit orfunctional portion or fragment thereof.

In accordance with still another embodiment, the present inventionprovides a multimeric molecule comprising a heavy chain immunoglobulinfragment of the VHH type described herein, in which VHH sequences arefused to yield multimeric units of 2 or more VHH units optionally linkedvia a spacer molecule.

In accordance with a further embodiment, the present invention providesa multimeric molecule comprising two or more VHH sequences describedherein, which are fused to yield 2, 3, 4 or 5 or more VHH unitsoptionally linked via a spacer molecule.

In accordance with an embodiment, the present invention provides anucleic acid encoding a heavy chain immunoglobulin fragment of the VHHtype and having affinity for envelope proteins of HIV-1 which iscovalently linked to the P. aeruginosa Exotoxin A subunit comprising thenucleic acid sequence of SEQ ID NO: 6.

In accordance with a further embodiment, the present invention providesan expression vector comprising the gene encoding the heavy chainimmunoglobulin fragment and having affinity for envelope proteins ofHIV-1 which is covalently linked to the P. aeruginosa Exotoxin A subunitor functional portion or fragment thereof.

In accordance with an embodiment, the present invention provides amethod for the therapy or prophylaxis of HIV-1 infection, comprisingadministering to a patient a heavy chain immunoglobulin or fragmentthereof having affinity for envelope proteins of HIV-1 which iscovalently linked to the P. aeruginosa Exotoxin A subunit or functionalportion or fragment thereof, or the multimeric molecule of describedherein.

In accordance with another embodiment, the present invention provides amethod for the therapy or prophylaxis of HIV-1 infection, comprisingadministering to a patient a micro-organism expressing the heavy chainimmunoglobulin or fragment thereof and having affinity for envelopeproteins of HIV-1 or an antigen thereof that is covalently linked to theP. aeruginosa Exotoxin A subunit or functional portion or fragmentthereof, or the multimeric molecule described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the structural comparison of human and camelidantibodies and antibody fragments. Adapted from Holliger & Hudson 2005.

FIG. 2 depicts purification of gD2 From Pichia pastoris. A) Amino acids1-314 of gD2 were amplified by PCR from the HSV-2 strain 186 genome. Band C) Purified gD2 from Pichia pastoris was separated by SDS-PAGE andstained with Coomassie (B) or transferred to PVDF membrane and detectedwith a polyclonal anti-gD2 antibody (R45) by Western blotting (C).

FIG. 3 shows antibody reactivity to purified gD2 (ELISA). ELISA wellswere coated with gD2 and detected with a panel of anti-gD2 antibodies:R45 (rabbit, polyclonal), HSV8 (human, monoclonal), DL6 (mouse,monoclonal), anti-His (mouse, monoclonal). Additionally wells coatedwith gD2 where only HRP-conjugated secondary antibody (anti-rabbit,anti-human, and anti-mouse) was added were run as controls.

FIG. 4 depicts llama serum ELISA. Llama serum collected before theinitiation of immunization (naïve) and after each immunization (Im#1-5)was diluted 1:10,000 and used to coat ELISA wells. gD2 was added andbinding was detected to determine if the llamas mounted an immuneresponse against the gD2 immunizations.

FIG. 5 shows a llama serum neutralization assay. Naïve llama serum andllama serum following the 4^(th) and 5^(th) immunizations was seriallydiluted and incubated with HSV-2 for 1 hour at 37° C. before adsorptionon Vero cells for 1 hour. After overlay with methylcellulose andincubation for 2 days, cells were stained and plaques counted. Eachdilution was assayed in duplicate and error bars represent maximum andminimum percent values. Results were expressed as percent neutralizationcompared to naïve serum.

FIG. 6 depicts amplification of VHH regions from llama DNA. After thefinal immunization, PBMCs were separated from whole blood and RNA waspurified for synthesis of cDNA. Nested primer sets were used to amplifythe variable region from heavy chain only antibodies (VHH) from thecDNA, and PCR products were separated by agarose gel electrophoresis.Labels indicate which llama and round of PCR the sample is derived from.

FIG. 7 shows biopanning of VHH-Phage Library on gD2. After each round ofbiopanning, the eluted phage were titered to monitor the concentrationof phage during the biopanning process. The large drop in phage titerafter the first round of biopanning was expected, as most of theVHH-phage in the library are not specific for gD2. Subsequent rounds ofbiopanning show increased phage concentration as enrichment for gD2specific VHH-phage occurs.

FIG. 8 is a flowchart diagramming the process of identifying unique VHHsequences that bind to gD2. Individual phage clones were amplified andtested by ELISA to determine if they are reactive to gD2. Those thatwere reactive were sequenced, and the sequences were compared todetermine the number of unique VHH sequences.

FIG. 9 shows VHH-Phage Binding to gD2. VHH-phage clones after multiplerounds of biopanning were individually amplified and tested forreactivity to gD2 by ELISA. Wells were coated with gD2, VHH-phage cloneswere added and then detected with an anti-phage antibody. The six uniqueVHH from Llama No: 2 (R1, R15, R17, R18, R33, and R39), four unique VHHfrom Llama No: 1 (P1, P3, P4, and P15), and one non-gD2 bindingVHH-phage (P10) were tested.

FIG. 10 illustrates antibody capture biopanning. A) Conceptual diagramof how capture biopanning immobilizes gD2 through binding to aparticular epitope, thereby promoting selection of sVHH-phage that bindto other sites of gD2. B) The eluted phage after each round ofbiopanning were titered to monitor the concentration of phage during thebiopanning process.

FIG. 11 shows the results of antibody capture biopanning VHH-PhageELISA. VHH-phage clones after three rounds of capture biopanning wereindividually amplified and tested for reactivity to gD2 by ELISA. Wellswere coated with gD2 and VHH-phage clones were added and then detectedwith an anti-phage antibody. Previously identified VHH-phage were usedas positive (R33 and P4) and negative (P10) controls. The anti-gD2antibody DL6 was also used as a positive control. Each VHH-phage wasassayed in duplicate and error bars represent maximum and minimumvalues.

FIG. 12 illustrates a unique VHH amino acid sequence alignment. VHHinserts, originally amplified from variable region of heavy chain onlyantibodies, were sequenced from VHH-phage clones and aligned todetermine unique VHH sequences identified from the gD2 biopanningprocess.

FIG. 13 depicts expression and purification of VHH from E. coli. A) E.coli were transformed with VHH/pET plasmids and small scale cultureswere grown and induced to determine solubility of VHH proteins. Arepresentative gel demonstrating that VHH derived from one llama arelocated in the pellet (P), while VHH derived from a second llama arelocated in both the supernatant (SN) and the pellet. B) A representativegel demonstrated the size and purity of purified R33 and bvR33.

FIG. 14 shows that purified VHH bind to gD2. ELISAs were performed inwhich wells were coated with VHH and gD2 was added to assay for theirability to bind gD2. Each dilution was assayed in duplicate and errorbars represent maximum and minimum values.

FIG. 15 depicts VHH binding to gD2-expressing cell line. To determine ifVHH could bind to gD2 expressed at the cell surface, z4/6 cells (surfaceexpression of gD2) were stained with various VHH (C: R33, D: P4, E:bvR33, F: R15) and detected by a FITC-conjugated secondary antibody. DL6was used as a positive control to verify that gD2 was expressed (A), anda secondary antibody control with no VHH or primary antibody was alsoused as a negative control (B).

FIG. 16 depicts the purification of pentavalent VHH. R33 expressed as afusion protein with the verotoxin B subunit (NR33), allowing forpentamerization, were purified from transformed E. coli and separated bySDS-PAGE for staining with Coomassie to determine size and purity. Upondialysis, the monomers self-assemble in to a pentamer.

FIG. 17 shows the VHH neutralization of HSV-2 using the presentinvention. Virus was incubated with dilutions of VHH for 1 hour at 37°C. and then plated on Vero cells to assay for VHH neutralizing activity.Each dilution was assayed in duplicate and error bars represent maximumand minimum plaque numbers. Results are expressed as percent inhibitioncompared to plaque numbers from untreated virus. Statisticalsignificance compared to untreated virus was calculated by ANOVA and isindicated by asterisks (P<0.05). The known neutralizing antibody HSV8was used in graph A as a positive control.

FIG. 18 shows VHHExoA were purified from the insoluble fraction ofinduced E. coli cells and refolded according to previously publishedprotocols.

FIG. 19 illustrates that VHH and VHHExoA Bind to gD2. A capture ELISAwas performed to determine if the VHH portion of R33ExoA is able to bindgD2 when expressed with a C-terminal exotoxin A. Each dilution wasassayed in duplicate and error bars represent maximum and minimumvalues.

FIG. 20 shows the toxicity of VHHExoA on Vero cells and z4/6 cells. 20A)Dilutions of VHH-ExoA proteins were added to Vero cells (do not expressgD2) and their cytotoxicity was measured by addition of MTS reagent(Promega, Madison, Wis.). Triton X-100 was added at 0.05% to the firstdilution to serve as a positive control for cytotoxicity, and it dilutedas the other samples were. Dilutions of each protein were added to wellsin triplicate and error bars represent standard deviation. 20B)Dilutions of VHH-ExoA proteins were added to z4/6 cells (express gD2)and their cytotoxicity was measured by addition of MTS reagent (Promega,Madison, Wis.). Triton X-100 was added at 0.05% to the first dilution toserve as a positive control for cytotoxicity, and it diluted as theother samples were. Dilutions of each protein were added to wells intriplicate and error bars represent standard deviation.

FIG. 21 provides results of a VHHExoA infectious center assay. HSV-2infected Vero cells were treated with dilutions of VHHExoA, R33, or PBSfor about 16 hours. Infected cells were then harvested and diluted inuninfected Vero cells to assay for the number of infectious centers thatremain. This is a representative graph from four independentexperiments. Error bars represent standard error of the mean.

FIG. 22 depicts a nucleic acid sequence (22A) and an amino acid sequence(22B) for an embodiment of the VHHR33ExoA construct of the presentinvention.

FIG. 23 depicts a nucleic acid sequence (23A) and an amino acid sequence(23B) for an embodiment of the J3VHHExoA construct of the presentinvention.

FIG. 24 depicts the amino acid sequence of an embodiment of the presentinvention comprising fully expressed J3VHH construct (SEQ ID NO: 11) andthe J3VHHExoA construct (SEQ ID NO: 12). The figures show the annotatedprotein sequence of insert containing J3 VHH fused to Exotoxin A Key:Gray highlight signifies the start codon; Purple Highlight is the HisTag; Highlighted yellow regions contain restriction sites; 5′ end EcoR1;3′ end AvrII; Underlined sequence is the J3 VHH; Italicized sequence isthe linker region; Includes yellow highlighted multiple cloning sitesequence; Includes myc tag highlighted in blue; Bold sequence is the P.aeruginosa Exotoxin A subunit; Red highlight is the stop codon.

FIG. 25 depicts cell viability graphs showing the viability of CHO cellsexpressing or not expressing envelope after exposure to either the J3VHH or J3 VHH fused to exotoxin A.

FIG. 26 shows the relative neutralizing capability of J3 and J3ExoA.HIV-1 AD8 virus were produced from 293T cells and incubated withindicated concentration of J3 or J3ExoA for 1 h, and then infectedMAGI-CCR-5 cells. Viral infection was determined by MAGI assay. Theinfectivity of AD8 in absence of any protein was set as 100%.

FIG. 27 shows Relative ability of 50 nM J3 and J3ExoA to reduce viralload in PBMC culture when exposed to cells pre-infected with HIV_(BaL).

DETAILED DESCRIPTION OF THE INVENTION

In accordance with an embodiment, the present invention provides a heavychain immunoglobulin of the VHH type or fragment thereof having an aminoacid sequence of at least 85% identity to SEQ ID NO. 3 (R33) and havingaffinity for glycoprotein D 2 (gD2) of HSV-2 or antigen thereof.

As used herein, the term “heavy chain immunoglobulin of the VHH type orfragment thereof” means the variable domain of heavy-chain onlyantibodies found in members of the camelid family, and which representsthe smallest naturally occurring functional domain of the antibodymolecule. These variable domains, termed VHH, have the same antigenbinding capability as full-length antibodies, yet are typically around15 kDa in size. As a result of their small size, VHH have enhancedtissue penetration, and an extended CDR3 loop allows VHH access tocryptic epitopes in enzymatically active sites that are unavailable forbinding by full length antibodies.

VHH can act as a monomeric domain, or they can be expressed in amultivalent context to increase avidity and activity. Additionally,bispecific VHH can be assembled that bind different epitopes, which canin some cases dramatically increasing neutralization efficacy.

VHH can also serve as carriers for other molecules through conjugationor expression as a fusion protein with an effector domain to create animmunoconjugate.

As used herein, the term “immunoconjugate” is a conjugate of a bindingmolecule (e.g., an antibody) with an atom, molecule, or a higher-orderedstructure (e.g., with a liposome), and an antigen, and/or therapeuticagent, and/or a diagnostic agent.

The term “antigen” or “antigenic epitope” as used herein refers to anymolecule (e.g., protein, peptide, lipid, carbohydrate, etc.) solely orpredominantly expressed or over-expressed by a target cell of interest,such that the antigen is associated with the target cell.

In accordance with another embodiment, the present invention provides aheavy chain immunoglobulin of the VHH type or fragment thereof having anamino acid sequence of at least 85% identity to SEQ ID NO. 4 (R33) andhaving affinity for glycoprotein D 2 (gD2) of HSV-2 or antigen thereofthat is covalently linked to the P. aeruginosa Exotoxin A subunit.

The term “polypeptide” as used herein includes oligopeptides and refersto a single chain of amino acids connected by one or more peptide bonds.

The term “a peptide or polypeptide fragment thereof, capable of beingcleaved by a specific protease” as used herein, means an amino acidsequence which is specifically recognized by a protease enzyme andspecifically binds and hydrolytically cleaves that amino acid sequence.The peptide sequence can be any sequence of between about 3 to about 20amino acids in length, which is known to be cleaved by a known protease.In one or more embodiments, the present invention provides animmunoconjugate where the peptide or polypeptide fragment thereof,capable of being cleaved by a specific protease is an amino acidsequence cleaved by a protease normally found on cancer cell membranes.Preferably, the protease is furin, which is found on many types of tumorcells.

The term “functional portion” when used in reference to a monoclonalantibody or antigenic epitope refers to any part or fragment, which partor fragment retains the biological activity of which it is a part (theparent molecule, antibody, or antigen). Functional portions encompass,for example, those parts that retain the ability to specifically bind tothe antigen (e.g., in an MHC-independent manner), or detect, treat, orprevent the disease, to a similar extent, the same extent, or to ahigher extent, as the parent molecule. In reference to the parentmolecule, the functional portion can comprise, for instance, about 10%,25%, 30%, 50%, 68%, 80%, 90%, 95%, or more, of the parent molecule.

The functional portion can comprise additional amino acids at the aminoor carboxy terminus of the portion, or at both termini, which additionalamino acids are not found in the amino acid sequence of the parentmolecule. Desirably, the additional amino acids do not interfere withthe biological function of the functional portion, e.g., specificallybinding to a cancer antigen, having the ability to detect cancer, treator prevent cancer, etc. More desirably, the additional amino acidsenhance the biological activity, as compared to the biological activityof the parent molecule.

By “protein” is meant a molecule comprising one or more polypeptidechains.

In this regard, the invention also provides an immunoconjugate moleculecomprising at least one of the polypeptides described herein along withat least one other polypeptide. The other polypeptide can exist as aseparate polypeptide of the fusion protein, or can exist as apolypeptide, which is expressed in frame (in tandem) with one of theinventive polypeptides described herein. The other polypeptide canencode any peptidic or proteinaceous molecule, or a portion thereof.Suitable methods of making fusion proteins are known in the art, andinclude, for example, recombinant methods. See, for instance, Choi etal., Mol. Biotechnol. 31: 193-202 (2005).

As used herein, “recombinant antibody” refers to a recombinant (e.g.,genetically engineered) protein comprising at least one of thepolypeptides of the invention and a polypeptide chain of an antibody, ora portion thereof. The polypeptide of an antibody, or portion thereof,and is a heavy chain immunoglobulin of the VHH type or fragment thereof.The polypeptide chain of an antibody, or portion thereof, can exist as aseparate polypeptide of the recombinant antibody. Alternatively, thepolypeptide chain of an antibody, or portion thereof, can exist as apolypeptide, which is expressed in frame (in tandem) with thepolypeptide of the invention. The polypeptide of an antibody, or portionthereof, can be a polypeptide of any antibody or any antibody fragment,including any of the antibodies and antibody fragments described herein.

In accordance with an embodiment, the VHH portion of the immunoconjugatecan be directed to other well-known proteins highly expressed on othertarget cells when compared to normal cells in the body. Examples of suchproteins include, without limitation, envelope proteins of HIV-1 andothers known in the art.

In accordance with another embodiment, the present invention provides aheavy chain immunoglobulin of the VHH type or fragment thereofcomprising an amino acid sequence of at least 85% identity to SEQ IDNOS. 7 or 11, and having affinity for envelope proteins of HIV-1.

In accordance with yet another embodiment, the present inventionprovides a heavy chain immunoglobulin of the VHH type or fragmentthereof comprising an amino acid sequence of at least 85% identity toSEQ ID NOS. 8 or 12, and having affinity for envelope proteins of HIV-1which is covalently linked to the P. aeruginosa Exotoxin A subunit orfunctional portion or fragment thereof.

Included in the scope of the invention are functional variants of theinventive immunoconjugate, and polypeptides, and proteins describedherein. The term “functional variant” as used herein refers to animmunoconjugate, polypeptide, or protein having substantial orsignificant sequence identity or similarity to a parent immunoconjugate,polypeptide, or protein, which functional variant retains the biologicalactivity of the immunoconjugate, polypeptide, or protein of which it isa variant. In reference to the parent immunoconjugate, polypeptide, orprotein, the functional variant can, for instance, be at least about30%, 50%, 75%, 80%, 90%, 98% or more identical in amino acid sequence tothe parent immunoconjugate, polypeptide, or protein.

The functional variant can, for example, comprise the amino acidsequence of the parent immunoconjugate, polypeptide, or protein with atleast one conservative amino acid substitution. Conservative amino acidsubstitutions are known in the art, and include amino acid substitutionsin which one amino acid having certain physical and/or chemicalproperties is exchanged for another amino acid that has the samechemical or physical properties. For instance, the conservative aminoacid substitution can be an acidic amino acid substituted for anotheracidic amino acid (e.g., Asp or Glu), an amino acid with a nonpolar sidechain substituted for another amino acid with a nonpolar side chain(e.g., Ala, Gly, Val, Ile, Leu, Met, Phe, Pro, Trp, Val, etc.), a basicamino acid substituted for another basic amino acid (Lys, Arg, etc.), anamino acid with a polar side chain substituted for another amino acidwith a polar side chain (Asn, Cys, Gln, Ser, Thr, Tyr, etc.), etc

Alternatively or additionally, the functional variants can comprise theamino acid sequence of the parent immunoconjugate, polypeptide, orprotein with at least one non-conservative amino acid substitution. Inthis case, it is preferable for the non-conservative amino acidsubstitution to not interfere with or inhibit the biological activity ofthe functional variant. Preferably, the non-conservative amino acidsubstitution enhances the biological activity of the functional variant,such that the biological activity of the functional variant is increasedas compared to the parent immunoconjugate, polypeptide, or protein.

The immunoconjugate, polypeptide, and/or protein of the invention(including functional portions and functional variants thereof) can beobtained by methods known in the art. Suitable methods of de novosynthesizing polypeptides and proteins are described in references, suchas Chan et al., Fmoc Solid Phase Peptide Synthesis, Oxford UniversityPress, Oxford, United Kingdom, 2005; Peptide and Protein Drug Analysis,ed. Reid, R., Marcel Dekker, Inc., 2000; Epitope Mapping, ed. Westwooodet al., Oxford University Press, Oxford, United Kingdom, 2000; and U.S.Pat. No. 5,449,752. Also, polypeptides and proteins can be recombinantlyproduced using the nucleic acids described herein using standardrecombinant methods. See, for instance, Sambrook et al., MolecularCloning: A Laboratory Manual, 3rd ed., Cold Spring Harbor Press, ColdSpring Harbor, N.Y. 2001; and Ausubel et al., Current Protocols inMolecular Biology, Greene Publishing Associates and John Wiley & Sons, NY, 1994. Further, some of the immunoconjugates, polypeptides, andproteins of the invention (including functional portions and functionalvariants thereof) can be isolated and/or purified from a source, such asa plant, a bacterium, an insect, a mammal, e.g., a rat, a human, etc.Methods of isolation and purification are well-known in the art.Alternatively, the immunoconjugates, polypeptides, and/or proteinsdescribed herein (including functional portions and functional variantsthereof) can be commercially synthesized by companies, such as Synpep(Dublin, Calif.), Peptide Technologies Corp. (Gaithersburg, Md.), andMultiple Peptide Systems (San Diego, Calif.). In this respect, theinventive immunoconjugates, polypeptides, and proteins can be synthetic,recombinant, isolated, and/or purified.

In accordance with yet another embodiment, the present inventionprovides a nucleic acid molecule which encodes the immunoconjugatesdescribed above.

For example, the present invention includes nucleic acid moleculescomprising SEQ ID NOS: 1, 2, 5 and 6.

Further provided by the invention is a nucleic acid comprising anucleotide sequence encoding any of the immunoconjugates, polypeptides,or proteins described herein (including functional portions andfunctional variants thereof).

By “nucleic acid” as used herein includes “polynucleotide,”“oligonucleotide,” and “nucleic acid molecule,” and generally means apolymer of DNA or RNA, which can be single-stranded or double-stranded,synthesized or obtained (e.g., isolated and/or purified) from naturalsources, which can contain natural, non-natural or altered nucleotides,and which can contain a natural, non-natural or altered internucleotidelinkage, such as a phosphoroamidate linkage or a phosphorothioatelinkage, instead of the phosphodiester found between the nucleotides ofan unmodified oligonucleotide. It is generally preferred that thenucleic acid does not comprise any insertions, deletions, inversions,and/or substitutions. However, it may be suitable in some instances, asdiscussed herein, for the nucleic acid to comprise one or moreinsertions, deletions, inversions, and/or substitutions.

Preferably, the nucleic acids of the invention are recombinant. As usedherein, the term “recombinant” refers to (i) molecules that areconstructed outside living cells by joining natural or synthetic nucleicacid segments to nucleic acid molecules that can replicate in a livingcell, or (ii) molecules that result from the replication of thosedescribed in (i) above. For purposes herein, the replication can be invitro replication or in vivo replication.

The nucleic acids can be constructed based on chemical synthesis and/orenzymatic ligation reactions using procedures known in the art. See, forexample, Sambrook et al., supra, and Ausubel et al., supra. For example,a nucleic acid can be chemically synthesized using naturally occurringnucleotides or variously modified nucleotides designed to increase thebiological stability of the molecules or to increase the physicalstability of the duplex formed upon hybridization (e.g.,phosphorothioate derivatives and acridine substituted nucleotides).Examples of modified nucleotides that can be used to generate thenucleic acids include, but are not limited to, 5-fluorouracil,5-bromouracil, 5-chlorouracil, 5-iodouracil, hypoxanthine, xanthine,4-acetylcytosine, 5-(carboxyhydroxymethyl) uracil,5-carboxymethylaminomethyl-2-thiouridine,5-carboxymethylaminomethyluracil, dihydrouracil,beta-D-galactosylqueosine, inosine, N6-isopentenyladenine,1-methylguanine, 1-methylinosine, 2,2-dimethylguanine, 2-methyladenine,2-methylguanine, 3-methylcytosine, 5-methylcytosine, N6-substitutedadenine, 7-methylguanine, 5-methylaminomethyluracil,5-methoxyaminomethyl-2-thiouracil, beta-D-mannosylqueosine,5′-methoxycarboxymethyluracil, 5-methoxyuracil,2-methylthio-N6-isopentenyladenine, uracil-5-oxyacetic acid (v),wybutoxosine, pseudouracil, queosine, 2-thiocytosine,5-methyl-2-thiouracil, 2-thiouracil, 4-thiouracil, 5-methyluracil,uracil-5-oxyacetic acid methylester, 3-(3-amino-3-N-2-carboxypropyl)uracil, and 2,6-diaminopurine. Alternatively, one or more of the nucleicacids of the invention can be purchased from companies, such asMacromolecular Resources (Fort Collins, Colo.) and Synthegen (Houston,Tex.).

In some embodiments, the substituted nucleic acid sequence may beoptimized. Without being bound to a particular theory, it is believedthat optimization of the nucleic acid sequence increases the translationefficiency of the mRNA transcripts. Optimization of the nucleic acidsequence may involve substituting a native codon for another codon thatencodes the same amino acid, but can be translated by tRNA that is morereadily available within a cell, thus increasing translation efficiency.Optimization of the nucleic acid sequence may also reduce secondary mRNAstructures that would interfere with translation, thus increasingtranslation efficiency.

The invention also provides an isolated or purified nucleic acidcomprising a nucleotide sequence which is complementary to thenucleotide sequence of any of the nucleic acids described herein or anucleotide sequence which hybridizes under stringent conditions to thenucleotide sequence of any of the nucleic acids described herein.

In accordance with still a further embodiment, the present inventionprovides a plasmid which comprises a nucleic acid molecule which encodesthe immunoconjugates described herein. In accordance with someembodiments, the plasmid constructs of the present invention

The nucleic acids of the invention can be incorporated into arecombinant expression vector. In this regard, the invention providesrecombinant expression vectors comprising any of the nucleic acids ofthe invention. For purposes herein, the term “recombinant expressionvector” means a genetically-modified oligonucleotide or polynucleotideconstruct that permits the expression of an mRNA, protein, polypeptide,or peptide by a host cell, when the construct comprises a nucleotidesequence encoding the mRNA, protein, polypeptide, or peptide, and thevector is contacted with the cell under conditions sufficient to havethe mRNA, protein, polypeptide, or peptide expressed within the cell.The vectors of the invention are not naturally-occurring as a whole.However, parts of the vectors can be naturally-occurring. The inventiverecombinant expression vectors can comprise any type of nucleotides,including, but not limited to DNA and RNA, which can be single-strandedor double-stranded, synthesized or obtained in part from naturalsources, and which can contain natural, non-natural or alterednucleotides. The recombinant expression vectors can comprisenaturally-occurring, non-naturally-occurring internucleotide linkages,or both types of linkages. Preferably, the non-naturally occurring oraltered nucleotides or internucleotide linkages do not hinder thetranscription or replication of the vector.

The recombinant expression vector of the invention can be any suitablerecombinant expression vector, and can be used to transform or transfectany suitable host. Suitable vectors include those designed forpropagation and expansion or for expression or both, such as plasmidsand viruses. The vector can be selected from the group consisting of thepUC series (Fermentas Life Sciences), the pBluescript series(Stratagene, LaJolla, Calif.), the pET series (Novagen, Madison, Wis.),the pGEX series (Pharmacia Biotech, Uppsala, Sweden), and the pEX series(Clontech, Palo Alto, Calif.). Bacteriophage vectors, such as λGT10,λGT11, λZapII (Stratagene), λEMBL4, and λNM1149, also can be used.Examples of plant expression vectors include pBI01, pBI101.2, pBI101.3,pBI121 and pBIN19 (Clontech). Examples of animal expression vectorsinclude pEUK-C1, pMAM and pMAMneo (Clontech). Preferably, therecombinant expression vector is a viral vector, e.g., a retroviralvector.

The recombinant expression vectors of the invention can be preparedusing standard recombinant DNA techniques described in, for example,Sambrook et al., supra, and Ausubel et al., supra. Constructs ofexpression vectors, which are circular or linear, can be prepared tocontain a replication system functional in a prokaryotic or eukaryotichost cell. Replication systems can be derived, e.g., from ColEl, 2μplasmid, λ, SV40, bovine papilloma virus, and the like.

Desirably, the recombinant expression vector comprises regulatorysequences, such as transcription and translation initiation andtermination codons, which are specific to the type of host (e.g.,bacterium, fungus, plant, or animal) into which the vector is to beintroduced, as appropriate and taking into consideration whether thevector is DNA- or RNA-based.

The recombinant expression vector can include one or more marker genes,which allow for selection of transformed or transfected hosts. Markergenes include biocide resistance, e.g., resistance to antibiotics, heavymetals, etc., complementation in an auxotrophic host to provideprototrophy, and the like. Suitable marker genes for the inventiveexpression vectors include, for instance, neomycin/G418 resistancegenes, hygromycin resistance genes, histidinol resistance genes,tetracycline resistance genes, and ampicillin resistance genes.

It will be understood by those of ordinary skill in the art that therecombinant vectors which can be used to express the immunoconjugates ofthe present invention can be used to transfect any species of bacteriathat are capable of colonizing the vagina or other orifices of the bodyof a subject. A common example of such a species of bacteria isLactobacillus, including, for example, L. jensenii, L. reuteri, L.gasseri, L. crispatus, and L. iners, or other lactobacillus orlactococcus species that may colonize the human vagina.

The recombinant expression vector can comprise a native or nonnativepromoter operably linked to the nucleotide sequence encoding theimmunoconjugate, polypeptide, or protein (including functional portionsand functional variants thereof), or to the nucleotide sequence which iscomplementary to or which hybridizes to the nucleotide sequence encodingthe immunoconjugate, polypeptide, or protein. The selection ofpromoters, e.g., strong, weak, inducible, tissue-specific anddevelopmental-specific, is within the ordinary skill of the artisan.Similarly, the combining of a nucleotide sequence with a promoter isalso within the skill of the artisan. The promoter can be a non-viralpromoter or a viral promoter, e.g., a cytomegalovirus (CMV) promoter, anSV40 promoter, an RSV promoter, and a promoter found in thelong-terminal repeat of the murine stem cell virus.

The antibody can be in monomeric or polymeric form. Also, the antibodyor fragments thereof, can have any level of affinity or avidity for thetarget cell or population of cell antigen(s). Desirably, the antibody isspecific for the functional portion of the target cell or population ofcells, such that there is minimal cross-reaction with other cells orpopulations of cells.

Methods for generating humanized antibodies are well known in the artand are described in detail in, for example, Janeway et al., supra, U.S.Pat. Nos. 5,225,539, 5,585,089 and 5,693,761, European Patent No.0239400 B1, and United Kingdom Patent No. 2188638. Humanized antibodiescan also be generated using the antibody resurfacing technologydescribed in U.S. Pat. No. 5,639,641 and Pedersen et al., J. Mol. Biol.,235, 959-973 (1994).

The invention also provides antigen binding portions of any of theantibodies described herein.

Also, the antibody, or antigen binding portion thereof, can be modifiedto comprise a detectable label, such as, for instance, a radioisotope, afluorophore (e.g., fluorescein isothiocyanate (FITC), phycoerythrin(PE)), an enzyme (e.g., alkaline phosphatase, horseradish peroxidase),and element particles (e.g., gold particles).

It will be understood by those of ordinary skill in the art that theembodiments of VHH linked immunotoxin can be used in multiple ways. Ifapplied vaginally, an anti-gD2 immunotoxin could prevent HSV-2 infectionby killing infected epithelial cells prior to establishment of latency.Thus, the immunotoxins of the present invention have the potential tonot only act as a microbicides to prevent initial infection, but canalso act to reduce viral shedding in infected individuals by eliminatinggD2-expressing cells during reactivation of the virus from latency.

In accordance with a further embodiment, the present invention providesa method for treating HSV2 in a subject, comprising administering to thesubject, a therapeutically effective amount of the immunoconjugatedescribed above and a pharmaceutically acceptable carrier.

In accordance with a further embodiment, the present invention providesa method for treating HIV-1 in a subject, comprising administering tothe subject, a therapeutically effective amount of the immunoconjugatedescribed above and a pharmaceutically acceptable carrier.

It will be understood by those of skill in the art that one of themechanisms by which HIV-1 and HIV-2 escape elimination by the hostimmune system is by the HIV-1 genome residing within resting or inactiveimmune cells without expressing viral proteins that can be recognized bythe immune system. One embodiment for curing HIV-1 infection would be toactivate those resting cells so that the virus then expresses proteinsthat will appear on the surface of the infected cells either as peptidesin association with MHC molecules or as native proteins which accumulateon the cell surface as part of the virus assembly process. Onceexpressed on the cell surface these proteins can serve as targets forimmunotoxins so that the infected cells can be eliminated. As such, anexample of compounds that might be used for activating resting cells andactivating latent virus would be histone deacetylation (HDAC)inhibitors. To be most effective against a broad range of HIV-1variants, a VHH exotoxin A fusion protein of the present inventionshould target a highly conserved region of the viral envelope, which istypically expressed on the surface of activated, HIV-1 expressing cells.A VHH with such broad specificity has been identified (J Exp Med209:1091-1103 (2012). In an embodiment, a method of treatment of HIVwould include administration of HDAC inhibitors to HIV-1 infected peoplewho are concurrently receiving antiretroviral therapy, and who wouldthen be administered the VHH exotoxin A of the present invention by theintravenous route using a dose of the preparation that would avoidnon-specific toxicity but would kill HIV infected cells expressing theconserved region of the envelope protein. The lack of non-specifictoxicity is attained by linking the toxin covalently to the VHH thatonly targets the toxin to infected cells.

In some embodiments, the binding affinity of the VHH will be enhanced byconverting it from a monovalent to a bivalent VHH (bvJ3). This will bedone, by using appropriate primer sets to amplify a second J3 sequenceand incorporate a GS linker between the two J3 sequences. DNA encodingthe 38 kd fragment of ExoA will then be cloned in frame to the Cterminus of the VHH. Using dilution series, we will then test therelative killing activity of the bvJ3-ExoA and J3-ExoA using the Env+and Env-CHO cell lines. The expectation is that the bvJ3-ExoA will beactive at lower concentrations. A similar construct will be developedusing the active fragment of diphtheria toxin.

In some other embodiments, due to the short in vivo half-life ofcirculating VHH, we can further modify these constructs by fusing themvia a linker sequence (such as GGGS) to DNA encoding the albumin bindingpeptide RLMEDICLPRWGCLWEDDF (ABP) (SEQ ID NO:). Previous studies withthis peptide have fused it to the C terminal end of scFv with resultinga 5-6 fold increase in the half-life of the associated protein. We willproduce constructs in which the peptide is placed with or without linkersequences before or after the ExoA component of the VHH-ExoA construct.Efficacy will again be studied using the Env+ and Env-CHO cell lines. Ifbioactivity of the albumin-binding construct is confirmed, its albuminbinding will be evaluated by ELISA, testing the binding of theABP-VHH-ExoA construct in wells coated with albumin vs. control wells,as described, using antibodies targeting the His-tag incorporated intothe VHH construct for ELISA development.

In accordance with some other embodiments, the exotoxin can beadministered subcutaneously by being incorporated into sustaineddelivery particles. For example, the Medusa® drug delivery platformconsists of proprietary depot hydrogels for the formulation and/or theextended release of a broad range of biologics (including proteins,antibodies, peptides and vaccines) and of small molecules (injectabledrugs). These hydrogels have been proven to be safe and biodegradable.Medusa enables the controlled delivery from 1 day up to 14 days ofnon-denatured or non-modified drugs that maintain full bioactivity. Thein vivo efficacy of the embodiments can be confirmed by Western blottingof serum obtained from mice at different time points post administrationof either the “native” J3-ExoA or J3-ExoA administered in an extendedrelease format.

The immunoconjugates of the present invention can be formulated into acomposition, such as a pharmaceutical composition. In this regard, theinvention provides a pharmaceutical composition comprising any of theimmunoconjugates, polypeptides, proteins, functional portions,functional variants, nucleic acids, expression vectors, and apharmaceutically acceptable carrier. The inventive pharmaceuticalcompositions containing any of the inventive immunoconjugates cancomprise more than one immunoconjugate.

Preferably, the carrier is a pharmaceutically acceptable carrier. Withrespect to pharmaceutical compositions, the carrier can be any of thoseconventionally used and is limited only by chemico-physicalconsiderations, such as solubility and lack of reactivity with theactive compound(s), and by the route of administration. Thepharmaceutically acceptable carriers described herein, for example,vehicles, adjuvants, excipients, and diluents, are well-known to thoseskilled in the art and are readily available to the public. It ispreferred that the pharmaceutically acceptable carrier be one which ischemically inert to the active agent(s) and one which has no detrimentalside effects or toxicity under the conditions of use.

The choice of carrier will be determined in part by the particularimmunoconjugate, as well as by the particular method used to administerthe immunoconjugate. Accordingly, there are a variety of suitableformulations of the pharmaceutical composition of the invention. Thefollowing formulations for aerosol, parenteral, subcutaneous,interperitoneal, vaginal and rectal, administration are exemplary andare in no way limiting. More than one route can be used to administerthe immunoconjugate, and in certain instances, a particular route canprovide a more immediate and more effective response than another route.For treatment of HSV2, the preferred route is vaginal.

It will be appreciated by one of skill in the art that, in addition tothe above-described pharmaceutical compositions, the immunoconjugate ofthe invention can be formulated as inclusion complexes, such ascyclodextrin inclusion complexes, or liposomes.

For purposes of the invention, the amount or dose of the immunoconjugateadministered should be sufficient to effect, e.g., a therapeutic orprophylactic response, in the subject or animal over a reasonable timeframe. For example, the dose of the immunoconjugate should be sufficientto bind to a target antigen, or detect, treat or prevent an infection ina period of from about 2 hours or longer, e.g., 12 to 24 or more hours,from the time of administration. In certain embodiments, the time periodcould be even longer. The dose will be determined by the efficacy of theparticular immunoconjugate and the condition of the animal (e.g.,human), as well as the body weight of the animal (e.g., human) to betreated. In some embodiments, multiple administrations of theimmunoconjugate can be required to effect elimination of the viralburden in the subject. For example, there may be an initial dosefollowed by a period of time where the viral or tumor burden ismonitored and then subsequent dosages of the immunoconjugate are givenin an iterative fashion.

The terms “treat,” and “prevent” as well as words stemming therefrom, asused herein, do not necessarily imply 100% or complete treatment orprevention. Rather, there are varying degrees of treatment or preventionof which one of ordinary skill in the art recognizes as having apotential benefit or therapeutic effect. In this respect, the inventivemethods can provide any amount of any level of treatment or preventionof cancer in a mammal. Furthermore, the treatment or prevention providedby the inventive method can include treatment or prevention of one ormore conditions or symptoms of the disease, e.g., cancer, being treatedor prevented. Also, for purposes herein, “prevention” can encompassdelaying the onset of the disease, or a symptom or condition thereof.

As used herein, the term “subject” refers to any mammal, including, butnot limited to, mammals of the order Rodentia, such as mice andhamsters, and mammals of the order Logomorpha, such as rabbits. It ispreferred that the mammals are from the order Carnivora, includingFelines (cats) and Canines (dogs). It is more preferred that the mammalsare from the order Artiodactyla, including Bovines (cows) and Swines(pigs) or of the order Perssodactyla, including Equines (horses). It ismost preferred that the mammals are of the order Primates, Ceboids, orSimoids (monkeys) or of the order Anthropoids (humans and apes). Anespecially preferred mammal is the human.

EXAMPLES Expression and Purification of Recombinant his-gD2 from Pichiapastoris

Using genomic DNA from HSV-2 186 as a template, amino acids 1-314 of gD2(ectodomain) were amplified from the viral genome using primers(forward) CCCGAATTCACCATGAAATACGCCTTAGCAGACCCCTCG (SEQ ID NO: 9) and(reverse)

(SEQ ID NO: 10) ATTGCGGCCGCGTTAatggtgatggtgatggtgCGGGTTGCTGGGGGC,which also added a His tag to the C-terminus. The gD2 sequence wascloned into the expression vector pPIC9 and transformed into Pichiapastoris by electroporation. A mid-scale culture (˜30 mL) of BufferedGlycerol-complex Media (BMGY) was inoculated with 500 μL of a gD2/P.pastoris glycerol stock and grown at 30° C. shaking at 225 rpm for ˜48hours, until the cultures reaches an OD₆₀₀ of 2-6. The culture was thendiluted in 700 mL of BMGY media and grown in a 2 L-baffled flask at 30°C. with shaking at 225 rpm until the OD₆₀₀ reached 50. Cells wereharvested in sterile centrifuge bottles at 2500 g for 20 minutes at roomtemperature (RT). To induce expression, the cell pellet was resuspendedin 200 mL of Buffered Methanol-complex Media (BMMY) and grown for 48hours at 30° C. with shaking at 225 rpm. Cells were harvested bycentrifugation at 1500-3000 g and supernatant was collected; 2 mL Ni-NTASuperflow Resin (QIAGEN, Valencia, Calif.) equilibrated in PBS was addedper 45 mL supernatant and rocked overnight at 4° C. Resin was collectedby centrifugation and washed three times with 50 mL PBS. gD2 was theneluted from the resin by adding 4×1 mL elution buffer (250 mM imidazolein PBS). Eluted gD2 was filtered through a 0.22-micron filter anddialyzed overnight against PBS. Protein concentration was measured usinga Bradford Assay (BioRad, Hercules, Calif.).

Detection of gD2 Purified from Pichia pastoris.

NUNC Maxisorp ELISA plates (Thermo Fisher Scientific Inc., Waltham,Mass.) were coated with 0.5 μg purified protein per well overnight at 4°C. Plate was blocked with 2% BSA in PBS for 30 minutes at RT. Primaryantibodies, including R45 (rabbit polyclonal, gift from R. Eisenberg andG. Cohen, University of Pennsylvania, Philadelphia), HSV8 (humanmonoclonal, gift from L. Zeitlin, Mapp BioPharmaceuticals, San Diego,Calif.), DL6 (mouse monoclonal, (Santa Cruz Biotechnology, Dallas,Tex.), and anti-His (mouse monoclonal, Sigma-Aldrich, St. Louis, Mo.),were diluted in PBS-T and added to appropriate wells in duplicate for 1hour at RT. Wells were washed 5× with 200 μL PBS-Tween 0.2% (PBS-T) perwell and appropriate HRP-conjugated secondary antibody (JacksonImmunoResearch, West Grove, Pa.) was diluted in PBS-T and added to wellsfor 1 hour at RT. Wells were washed 5× with 200 μL PBS-T per well anddeveloped using ABTS® ELISA HRP Substrate (KPL, Gaithersburg, Md.). Theplate was read at 405 nm using a BioTek Synergy HT Plate Reader(Winooski, Vt.).

Llama Immunizations.

The immunization of two llamas, Llama No: 1 and Llama No: 2, wasperformed by Triple J Farms in Bellingham, Wash. (Protocol #110,approved by Triple J Farms IACUC, USDA registered #91-R-0054). Theimmunizations occurred on days 0, 21, 42, 63, and 280. Each llama wasimmunized with 0.5 mg of gD2 per injection, mixed with Complete Freund'sAdjuvant for the first injection and incomplete Freund's Adjuvant forsubsequent injections. Prior to the first immunization and followingeach immunization, ˜20 mL of serum was collected to monitor for thepresence of anti-gD2 antibody. After the fourth and fifth immunizations,500 mL of blood was taken from each animal and peripheral bloodmononuclear cells (PBMCs) were purified using a Ficoll-Paque Plusgradient (GE Healthcare Life Sciences, Piscataway, N.J.). PBMCs werealiquoted and frozen at −80° C. until further use.

Llama Serum ELISA.

NUNC Maxisorp ELISA plates (Thermo Fisher Scientific Inc., Waltham,Mass.) were coated with 100 μl of gD2 at 10 μg/mL and incubated ON at 4°C. The plate was blocked with 2% BSA in PBS for 30 minutes at RT.Freshly thawed serum samples were diluted 1:10,000 in PBS and added induplicate to wells for 1 hour at RT. Wells were washed 5×200 μl PBS-Tper well and HRP-conjugated anti-llama secondary antibody (BethylLaboratories, Inc) was diluted 1:10,000 in PBS-T and added to wells for1 hour at RT. Wells were washed 5× with 200 μl PBS-T per well anddeveloped using ABTS® ELISA HRP Substrate (KPL, Gaithersburg, Md.). Theplate was read at 405 nm using a BioTek Synergy HT Plate Reader(Winooski, Vt.).

Llama Serum Neutralization Assay.

Vero cells were plated in Falcon 12-well trays (Thermo Fisher ScientificInc., Waltham, Mass.) at 4×10⁶ cells per tray and incubated ON at 37° C.Llama serum samples were heat inactivated at 56° C. for 60 minutes andserial two-fold dilutions were made in DMEM/2% FBS. Approximately 5000pfu/mL of HSV-2 G was added to each dilution and all dilutions wereincubated at 37° C. for 1 hour. Media was removed from the Vero cellsand the serum dilutions with virus were added in duplicate to cells for1 hour at 37° C., with gentle shaking every ten minutes to distributevolume over cells. The inoculum was then removed from cells and cellswere overlaid with 2 mL 2% methylcellulose overlay/5% FBS in DMEM(Cellgro, Manassas, Va.). Trays were incubated for 3 days at 37° C.,stained with crystal violet, and plaques were counted.

Amplification of VHH Regions and Construction of T7 Phage DisplayLibrary.

Using PBMCs that were isolated following the fourth (Llama No: 2) orfifth immunization, RNA was extracted using an RNeasy Mini Kit (QIAGEN,Valencia, Calif.) and reverse transcribed into DNA (SuperScript IIReverse Transcriptase, Invitrogen, Carlsbad, Calif.). Nested PCR wasperformed to amplify the VHH regions from the genomic DNA using primersthat bind to the conserved regions flanking the VHH genes. The firstround of PCR was performed with primers as previously published, whilethe second round of primers introduced the appropriate restriction sitesfor ligation into the phage genome. The VHH band of ˜450 base pairs wasgel extracted and ligated into pre-digested T7 phage vector arms asdescribed in the manufacturer's handbook (Novagen Inc., Madison, Wis.).The ligation reaction was packaged into the phage according to themanufacturer's protocol and titered to determine the diversity of thepackaged library prior to amplification. After amplification, thelibrary was aliquoted and stored at −80° C. until further use. VHHexpressed on the phage surface are referred to as VHH-phage.

Biopanning of VHH/T7 Library Against gD2.

For the first round of biopanning, 10⁹ pfu from the phage library wasadded to a well coated with 0.5 μg gD2 and incubated at room temperaturefor 1 hour. Wells were then washed 10 times with shaking for 1 minutewith tris-buffered saline (TBS) with 0.05% Tween (TBS-T) and 10 timeswith TBS. Bound phage were eluted using 200 μl of 1% SDS in TBSincubated on wells for 1 hour at room temperature. A sample of theeluted phage was used to titer the amount of phage present, and theremaining eluted phage were added to 50 mL of BLT5403 grown in LB/Amp atOD₆₀₀ 0.5 and shaken at 37° C. until lysis occurred. This phage lysatewas titered and used as the input for the next round of biopanning,which was carried out using the same procedure. Additional rounds ofbiopanning were performed against gD2 and individual plaques from thephage elution after the second (Llama No: 1) or sixth (Llama No: 2)round of biopanning were picked, amplified, and sequenced.

Antibody Capture Biopanning.

Antibody capture biopanning was performed based on a previouslypublished protocol (Proc Natl Acad Sci USA 92, 6439-6443 (1995)). It wascarried out as described above, except that the ELISA wells were firstcoated with the non-neutralizing gD2 capture antibody, DL6 (Santa CruzBiotechnology, Dallas, Tex.). After this coating step, gD2 was added andthen the biopanning protocol proceeded as described in the previoussection.

VHH-Phage ELISA.

An ELISA was performed to determine if individual VHH-phage clones couldbind to gD2. NUNC Maxisorp ELISA plates (Thermo Fisher Scientific Inc.,Waltham, Mass.) were coated with 0.5 μg gD2 per well and incubated ON at4° C. The plate was blocked for 1 hour with 2% BSA in PBS, and then 10⁹pfu of each phage clone was added in duplicate and incubated at RT for 1hour. After removing phage, the plate was washed 5×200 μL PBS-T perwell. Anti-T7 tail fiber monoclonal antibody (GE Healthcare LifeSciences, Piscataway, N.J.) was diluted to 1:1000 and added to each wellfor 1 hour at RT. After washing the plate 5×200 μL PBS-T per well,HRP-conjugated anti-mouse IgG secondary antibody (JacksonImmunoResearch, West Grove, Pa.) was added at 1:3000 and incubated at RTfor 1 hour. After a final wash of 5×200 μL PBS-T per well, 200 μL ofABTS® ELISA HRP Substrate (KPL, Gaithersburg, Md.) was added. The platewas read at 405 nm using a BioTek Synergy HT Plate Reader (Winooski,Vt.).

Cloning and Expression of VHH in E. coli.

VHH sequences were amplified from phage by PCR amplification using theprimers that introduced EcoRI and XhoI restriction sites for cloning into pET-47b (Novagen Inc., Madison, Wis.). Additional primer sets wereused to amplify VHH and insert a second VHH sequence with a GS linkerbetween them to make a bivalent VHH construct. The monovalent andbivalent VHH constructs were transformed in to BL21 DE3 competent cells(New England Biolabs, Ipswich, Mass.). Two methods of expression andpurification were utilized depending on the solubility of the VHHprotein.

1) Osmotic shock: For the VHH that were soluble (all VHH derived fromLlama No: 2, indicated by R##), an osmotic shock protocol was utilizedto purify protein from the periplasmic space, as described by Graef etal. (BMC Biotechnol 11, 86 (2011)). Briefly, an ON 30 mL mid-scaleculture was diluted in 450 mL Terrific Broth and grown at 25° C. for 3hours. Cells were induced at 1 mM IPTG (Lab Scientific, Inc, Highlands,N.J.) and grown for an additional 3 hours at 25° C. Aftercentrifugation, the cell pellet was lysed in Tris-sucrose buffer withlysozyme. Contents of periplasmic space were separated from cellulardebris by centrifugation and Ni-NTA Agarose (QIAGEN, Valencia, Calif.)was added to the supernatant ON with rocking at 4° C. Agarose wascollected by centrifugation and washed, and protein was eluted byaddition of 3 mL elution buffer.

2) Insoluble protein purification: For those VHH that were insoluble(all VHH derived from Llama No: 1, indicated by P##), an ON 10 mLculture was diluted into 750 mL of LB/Kan and grown until OD₆₀₀ 0.6-0.8.After induction with IPTG at 1 mM for 3 hours at 37° C., cells wereharvested by centrifugation at 3500 g for 30 minutes, resuspended in 10mL lysis buffer (6 M Guanidine hydochloride, 0.1 M NaH₂PO₄, 0.01 M Trisbase, 0.01 M imidazole, pH 8) and frozen at −80° C. for at least 30minutes. Upon thawing, the volume of the lysate was brought to 30 mLwith lysis buffer, incubated with rocking at RT for at least 30 minutes,and then centrifuged at 14000 rpm for 30 minutes. After the pellet wasdiscarded, Ni-NTA Agarose (QIAGEN, Valencia, Calif.) was added to lysateand rocked at RT for 1 hour or ON at 4° C. Beads were washed twice with7 mL Wash Buffer 1 (8 M urea, 0.1 M NaH₂PO₄, 0.15 M NaCl, 0.02 Mimidazole, pH 8) and then washed with ˜50 mL (7×7 mL) Wash Buffer 2(0.05 M NaH₂PO₄, 0.5 M NaCl, 0.02 M imidazole, pH 8). To elute VHH frombeads, 4×1 mL Elution Buffer (0.05 M NaH₂PO₄, 0.5 M NaCl, 0.25 Mimidazole, pH 8) was added for 1 hour at RT.

For both protein purification methods, eluted VHH were dialyzed againstPBS with 1 mM DTT with at least 4 buffer changes. VHH were concentratedwith Amicon Ultra-15 Centrifugal Filter Unit (EMD Millipore, Billerica,Mass.), centrifuged at 16,000×g for 10 minutes to remove precipitatedprotein, and protein concentration was measured by Bradford assay(BioRad, Hercules, Calif.).

Cloning and Expression of Pentavalent VHH.

To create a pentavalent VHH, the pVT2 plasmid was obtained from C. RogerMackenzie (National Research Council Canada, Ottawa, Ontario, Canada).This plasmid allows for cloning of VHH as a N-terminal fusion proteinwith the verotoxin B subunit, resulting in self-assembly in to apentamer (J Immunol Methods 318, 88-94 (2007)). R33 expressed as apentamer will be referred to as NR33. The pentavalent R33/pVT2 constructwas transformed into competent BL21 DE3 cells (New England Biolabs,Ipswich, Mass.) and expressed and purified as previously described (JMol Biol 335, 49-56 (2004)). Purified NR33 was run through a Superdex200column to verify self-assembly.

Coomassie and Western Blot of Purified gD2 and VHH.

To verify the size of purified protein, approximately 800 ng of gD2 oreach VHH sample was run on a SDS-PAGE gel for Commassie staining andapproximately 200 ng of each sample was run for a Western blot. ForWestern blotting, samples were transferred to polyvinyl difluoride(PVDF) membrane by a semi-dry transfer system (Biorad Trans-Blot SDSemi-Dry Transfer Cell, Hercules, Calif.) and detection was performedusing standard techniques. Briefly, PVDF membrane with transferredprotein was blocked with 5% milk for 1 hour at RT or ON at 4° C. Primaryantibody was diluted in PBS-T and incubated on blot for 1 hour at RTwith rocking. Blot was washed 4×10 minutes with PBS-T, andalkaline-phosphatase-conjugated secondary antibody (JacksonImmunoResearch Inc., West Grove, Pa.) was diluted in PBS-T and added toblot. After a final wash of 4×10 minutes in PBS-T, NBT (nitro-bluetetrazolium chloride) and BCIP (5-bromo-4-chloro-3′-indolyphosphatep-toluidine salt) detection reagents were added until bands werevisualized.

ELISA to Validate VHH Binding to gD2.

An ELISA was performed to determine if purified VHH bind to gD2. Wellsof NUNC Maxisorp ELISA plates (Thermo Fisher Scientific Inc., Waltham,Mass.) were coated with various dilutions of VHH made in PBS andincubated ON at 4° C. Purified gD2 diluted in PBS-T was added to wellsfor 1 hour at RT. Wells were washed 4×200 μL PBS-T and the anti-gDantibody DL6 (Santa Cruz Biotechnology, Dallas, Tex.) diluted in PBS-Twas added to detect gD2 binding by VHH. After a 1 hour incubation at RT,wells were washed again 5×200 μL PBS-T and an anti-mouse secondaryantibody conjugated to HRP (Jackson ImmunoResearch, West Grove, Pa.) wasadded. After a final wash with PBS-T 4×200 nL, 200 μL ABTS® ELISA HRPSubstrate (KPL, Gaithersburg, Md.) was added. The plate was read at 405nm using a BioTek Synergy HT Plate Reader (Winooski, Vt.).

Flow Cytometry to Validate VHH Binding to Surface Expressed-gD2.

Z4/6 cells (gift from D. Johnson, Oregon Health and Science University)are a derivative of L cells that stably express gD2 at the cell surface.Nearly confluent cells were trypsinized, washed once with PBS, andresuspended at 0.5×10⁶ cells/mL. 500 μL of cells were aliquoted,centrifuged at 500 g for 5 minutes, and resuspended with 1 mL 1% BSA/PBSand incubated at 37° C. for 30 minutes for blocking. Samples werecentrifuged at 500 g for 5 minutes, resuspended in VHH or DL6 antibody(Santa Cruz Biotechnology, Dallas, Tex.) diluted in 1% BSA/PBS, andincubated for 1 hour at 4° C. Cells were washed twice with 2 mL PBS andresuspended in appropriate FITC-conjugated secondary antibody (JacksonImmunoResearch, West Grove, Pa.) diluted in 1% BSA/PBS for 30 minutes at4° C., followed by a final wash with 2 mL PBS. Samples were run on aBecton-Dickinson FACSCalibur Cytometer and data was analyzed using FloJo(Tree Star Inc., Ashland, Oreg.).

VHH sequences were amplified using primers to introduce the appropriaterestriction sites for cloning into the pLEX plasmid, as well as tointroduce an N-terminal His tag and C-terminal myc tag.

HSV-2 Neutralization Assay with VHH

Vero cells were plated in Falcon 12-well trays (Thermo Fisher ScientificInc., Waltham, Mass.) at 4×10⁶ cells per tray and incubated overnight at37° C. VHH samples (monovalent, bivalent, and pentavalent) were seriallydiluted in DMEM/2% FBS with HSV-2 G (ATCC, Manassas, Va.) at 5×10³pfu/mL and all dilutions were incubated at 37° C. for 1 hour. Media wasremoved from the Vero cells and 100 μL of VHH dilutions with virus wereadded in duplicate to cells for 1 hour at 37° C., with gentle shakingevery ten minutes to distribute volume over cells. Cells were overlaidwith 2 mL of 2% methylcellulose overlay/5% FBS in DMEM (Cellgro,Manassas, Va.). Trays were incubated for 3 days at 37° C., stained withcrystal violet, and plaques were counted.

Testing VHH Vaginal HSV-2 Animal Challenge Model.

Six to eight week old female CF-1 were purchased from Harlan(Indianapolis, Ind.) and housed under reversed photoperiod conditions.As reported previously (BMC Infect Dis 6, 1471-2334 (2006)), mice areinjected subcutaneously in the hindquarters with 2.5 mg of Depo Provera(UpJohn Co. 400 mg/mL) seven days before the planned viral challenge. Onday seven, the VHH candidate and the viral inoculum of 10 ID₅₀ are mixedin a total volume of 20 μL and promptly delivered to the vagina with afire-polished Wiretrol pipet (Drummond Co., Broomall, Pa.). Three dayslater (Day 10) the vagina is lavaged using 20 μL of Bartel's TissueCulture Refeeding Media; the fluid is delivered vaginally and withdrawn10 to 20 times to collect HSV shed into the vagina. The lavage fluid iscentrifuged at 6500 rpm for 5 minutes to remove mucus and cells, andthen placed on human newborn foreskin cells to assay for presence ofvirus. Cells are observed by microscope 48 hours later and scored yes/nofor infection. Mice used in these studies were maintained in accordancewith the National Institutes of Health guidelines for the humane use oflaboratory animals. All experimental procedures involving mice wereapproved by the Institutional Animal Care and Use Committee of the JohnsHopkins University (Protocol Number MO12H147).

Expression, Purification, Refolding of VHHExoA.

A VHH that binds to gD2 of HSV-2 (called R33) was identified through themethods described above. P10, a VHH that does not bind to gD2 was alsoidentified (SEQ ID NO: xx). VHH sequences were amplified using primersthat introduced EcoRI and XhoI restriction sites for cloning in topET-47b (Novagen Inc., Madison, Wis.). The previously published exotoxinA sequence (Proc Natl Acad Sci USA 109, 11782-11787 (2012)) wassynthesized (GenScript, Inc, Piscataway, N.J.) and cloned in frame tothe C-terminus of the VHH (R33 and P10) already present in the pET-47bvector (SEQ ID NO:). Expression, purification, and refolding of VHHExoAproteins were performed based on a previously published protocol (AnalBiochem 205, 263-270 (1992)). Briefly, large-scale cultures (800 mL) oftransformed BL21 DE3 cells (New England Biolabs, Ipswich, Mass.) weregrown to OD₆₀₀ 0.6 and induced at 1 mM with IPTG (Lab Scientific, Inc,Highlands, N.J.) for 3 hours at 37° C. After cells were harvested andlysed under denaturing conditions (6 M GuHC1), Ni-NTA Agarose (QIAGEN,Valencia, Calif.) was added to the clarified lysate to purify theHis-tagged VHHExoA protein. After washing, VHHExoA protein was eluted (8M urea, 250 mM imidazole, 50 mM NaH₂PO4, 500 mM NaCl, 300 mM DTT)diluted 1:100 in refolding buffer (100 mM Tris, 500 mM L-arginine, 8 mMoxidized glutathione, 2 mM EDTA), and incubated at 10° C. overnight.After completion of the refolding reaction, the refolded VHHExoA wasconcentrated with an Amicon Ultra-15 Centrifugal Filter Unit (EMDMillipore, Billerica, Mass.) and buffer exchange was performed byrepeatedly bringing up the volume of the concentrated protein with PBS.The final volume of the protein was brought to ˜1 mL, aliquoted, andfrozen at −80° C. until use. Protein concentration was determined usinga Bradford assay (BioRad, Hercules, Calif.).

Toxicity Assay (MTS Assay). The CellTiter 96® AQueous One Solution CellProliferation Assay was used to determine toxicity of VHHExoA on celllines, and the assay was carried out using the protocol recommended bythe manufacturer (Promega, Madison, Wis.). Z4/6 cells, expressing gD2 atthe cell surface, and the parental L cell line were plated in 96-welltrays at 3×10⁵ cells/well overnight. The following day, dilutions of theVHHExoA proteins were added to wells and incubated overnight. About 16hours after the addition of protein, 20 μL of the CellTiter 96® AQueousOne Solution reagent was added to each well and incubated 4 hours at 37°C. Higher OD values indicate greater cell viability, and therefore, lesstoxicity. The plate was read at 490 nm with a BioTek Synergy HT PlateReader (Winooski, Vt.).

ELISA: Binding of VHHExoA to gD2. An ELISA was performed to determine ifthe purified VHHExoA was capable of binding to gD2. NUNC ELISA plateswere coated with dilutions of VHHExoA (0.25 μg/well), and after ablocking step, dilutions of purified gD2 were added to wells induplicate. After a washing step of 5×200 μL PBS-0.05% Tween (PBS-T) washbuffer, the anti-gD antibody DL6 (Santa Cruz Biotechnology, Dallas,Tex.) was added at 1:1000 for 1 hour. Wells were washed again andHRP-conjugated anti-mouse (Sigma-Aldrich, St. Louis, Mo.) was added at1:3000 for 1 hour. A final wash step was performed, and plate wasdeveloped by adding 100 μl/well ABTS® ELISA HRP Substrate (KPL,Gaithersburg, Md.). The plate was read at 405 nm using a BioTek SynergyHT Plate Reader (Winooski, Vt.).

In Vitro Infectious Center Assay (ICA)

Vero cells were plated in 12-well trays at 4×10⁶ cells/tray and after 24hours were infected with HSV-2 G (ATCC, Manassas, Va.) at 500 pfu/well.Following the 1 hour adsorption time, dilutions of the VHHExoA proteinswere added to wells in duplicate and complete media (DMEM, CellGro,Manassas, Va.) was added to bring volume up to 700 μL per well. About 16hours later, supernatant was removed and cells were trypsinized brieflywith 250 μL trypsin/EDTA (CellGro, Manassas, Va.) before adding an equalvolume of complete media. Cells were centrifuged at 500 g for 5 minutesto pellet cells, and then resuspended in 200 μL of complete media.Dilutions of the infected Vero cells were made in uninfected Vero cellsharvested the same day, and plated in 12-well trays so that total cellnumber was roughly 3×10⁵ cells/well. Cells were overlaid with 0.5%methylcellulose/5% FBS to bring volume to 1 ml. After 2 days, cells werestained with crystal violet and plaques were counted.

Animal Experiments. Six to eight week old female CF-1 were purchasedfrom Harlan (Indianapolis, Ind.) and housed under reversed photoperiodconditions. On Day 0 mice are injected subcutaneously in thehighquarters with 2.5 mg of Depo Provera (UpJohn Co. 400 mg/ml) one weekbefore the planned viral challenge. On Day 7, 10 μL of the virusinoculum (10 ID₅₀) is combined with 10 μL of the VHHExoA (20 μM,therefore final concentration is 10 μM) and 20 μL is promptly deliveredto the vagina with a fire-polished Wiretrol pipet (Drummond Co.,Broomall, Pa.). Six, 24, and 48 hours post challenge and, mice arevaginally treated with a 10 μL of 20 μM dose of VHHExoA. On Day 10 thevagina is lavaged using 20 μl of Bartel's Tissue Culture RefeedingMedia; the fluid is delivered vaginally and withdrawn 10 to 20 times tocollect HSV shed into the vagina. The lavage fluid is centrifuged at6500 rpm for 5 minutes to remove mucus and cells, and then placed onhuman newborn foreskin cells to assay for presence of virus. Cells areobserved by microscope 48 hours later (Day 13) and scored yes/no forinfection. All experimental procedures involving mice were approved bythe Institutional Animal Care and Use Committee of the Johns HopkinsUniversity (Protocol Number MO12H147).

Statistical Analysis. For the viral neutralization assays, thesignificance of the difference in plaque numbers was calculated using anANOVA test, with a Bonferroni correction (STATA Corp, College Station,Tex.). For analysis of the results from animal HSV-2 challengeexperiments, a Fisher exact test (two-tailed) was used to compare thenumber of animals infected between experimental and the control groups.

Example 1 Expression and Purification of Recombinant gD2 in Pichiapastoris

The extracellular domain of gD2 was amplified from the HSV-2 186 genome(FIG. 2A) and cloned in to the Pichia pastoris expression vector pPIC9for expression and purification (Protein Expression and Purification 25,400-408 (2002)). The size and purity of the purified gD2 was verified byseparation with SDS-PAGE and staining with Coomassie (FIG. 2B), as wellas by Western blot using a polyclonal anti-gD antibody (FIG. 2C). A bandapproximately 48 kDa was detected with both methods, somewhat smeareddue to the variable glycosylation pattern from P. pastoris, as has beenreported previously. gD2 was successfully detected by ELISA using apanel of conformation and non-conformational anti-gD2 antibodies (FIG.3), indicating that gD2 was successfully purified and suggests that itis folded correctly.

Example 2 Monitoring Antibody Response of gD2 Immunized Llamas

Two llamas, Llama No: 1 and Llama No: 2, were immunized five times withgD2, and after each immunization the animals were bled to obtain serumsamples. The induction of anti-gD2 antibodies was determined using anELISA. As shown in FIG. 4, serum from both llamas demonstratedreactivity to gD2 following the second immunization compared to serumcollected prior to immunization and after the first immunization. Thehighest reactivity to gD2 in serum collected from Llama No: 2 occurredafter the fourth immunization. Serum from Llama No: 1 had similarreactivity to gD2 as Llama No: 2, except there was a dramatic increasein gD2-reactivity following the last immunization (FIG. 4). In additionto the ability to bind gD2, the serum was also tested for the ability toneutralize HSV-2. While serum from Llama No: 2 had no significantneutralizing capability, Llama No: 1's serum obtained after the fourthand fifth immunizations generated IC₅₀ values of approximately 1:8 and1:256, respectively (FIG. 5). Taken together, these results indicatewhile both llamas did mount an antibody response against the gD2immunogen as measured by ELISA, only Llama No: 1 developed aneutralizing antibody response. This neutralizing response, however,does not guarantee that neutralizing VHH were induced, just that aneutralizing antibody response was generated.

Example 3 Construction of VHH/T7 Phage Display Library and BiopanningAgainst gD2

Based on the ELISA reactivity and neutralizing capability of the serum,VHH genes were amplified from cDNA generated from the PBMCs isolatedafter Llama No: 2's fourth immunization and Llama No: 1's fifthimmunization (FIG. 6). The amplified VHH genes were ligated into T7phage vector to generate libraries with initial diversities of 3.9×10⁷pfu for Llama No: 2 and 1.98×10⁷ pfu for Llama No: 1. For Llama No: 2,after the first round of biopanning, the titer of eluted phage increasedstepwise following each round of biopanning, indicating a gradualenrichment for VHH-phage binding to gD2 (FIG. 7). Titers of eluted phagefrom Llama No: 1's library, however, reached saturation after only tworounds of biopanning (FIG. 7), a pattern that was consistent despiterepeated attempts with different conditions (data not shown). This meantthat Llama No: 1's library was already dominated by a population ofphage reactive to gD2, and that further rounds of biopanning would notselect for additional unique VHH sequences.

Example 4 VHH-Phage Binding to gD2

Individual plaques from the phage elution after the second round ofbiopanning for Llama No: 1 and the sixth round of biopanning for LlamaNo: 2 were picked and amplified for analysis. Sixty VHH-phage cloneswere amplified from each llama and tested in an ELISA to determine ifthey can bind to gD2. For Llama No: 2, of the 60 VHH-phage tested, 56reacted to gD2 by ELISA (data not shown). After sequencing it wasdetermined that 91% of these sequences were identical (R33), and thatoverall there were 6 unique VHH sequences (FIG. 8). For Llama No: 1, ofthe 60 VHH-phage tested, there were 48 VHH-phage that reacted to gD2 byELISA (data not shown). Sequencing revealed that 94% of the VHHsequences were identical (P1), and that overall there were 4 unique VHHsequences (FIG. 8). A VHH-phage clone, called P10, that was amplifiedfrom Llama No: 1's library prior to any biopanning was also tested andsequenced for use as a negative control VHH-phage that did not bind togD2. A standardized VHH-phage ELISA with 10⁹ pfu per well was performedto determine relative reactivity to gD2 among the unique VHH isolated.All four of Llama No: 1's unique VHH-phage had higher reactivity to gD2than any of Llama No: 2's VHH-phage, although all of them were higherthan the negative control VHH-phage, P10 (FIG. 9).

Example 5 Antibody Capture Biopanning

Based on the antibody capture biopanning method described by Sanna etal., ELISA wells were coated with the non-neutralizing antibody DL6 inorder to capture gD2 by binding to one of its non-neutralizing epitopes(FIG. 10A). After the first round of biopanning (Llama No: 1's libraryonly), the titer of eluted phage increased over the next two rounds ofbiopanning (FIG. 10B), and plaques were picked after the third round tomonitor the VHH sequences. 40 VHH-phage plaques were picked and testedfor reactivity to gD2 by ELISA. Seventeen of these phage were able tobind gD2, and each of these phage were titered to perform a standardizedphage ELISA with 10⁹ pfu/well. As shown in FIG. 11, their reactivity togD2 was variable, but appeared to be higher than both R33/phage andP4/phage, which were run as positive controls. When the VHH genes weresequenced, however, all VHH sequences were identical to one of the 4previously identified phage from Llama No: 1.

Example 6 VHH Sequence Analysis

An alignment of all 10 unique sequences that bind to gD2, plus P10,reveals that they are indeed VHH sequences and that the hallmark VHHresidues are present (FIG. 12). Comparing the sequences from eachindividual llama however, reveals limited variation in the sequences.For example, there are only 11 amino acid differences among the sixunique VHH sequences for Llama No: 2, and only five of those amino aciddifferences occur in variable regions of the VHH that determine antigenspecificity (called CDR). Many of the amino acid differences areconserved within the same class of amino acids and therefore unlikely toaffect antigen binding. As a result, after determining that Llama No:2's VHH bind to gD2 at similar levels by ELISA (FIG. 14), we decided tofocus on R33, the majority sequence selected from biopanning.

Similarly, Llama No: 1's VHHs exhibit only five amino acid differences,several of which are conserved within the same class of amino acids.Based on the VHH-phage ELISA, we decided to proceed with P4, the VHHwith the highest reactivity to gD2 in the VHH-phage ELISA (FIG. 9).Llama No: 1's sequences, while certainly VHH sequences, are missingseveral canonical amino acid residues (F37, E44, R45, G47), particularlyin the very important framework 2 region (FR2). The FR2 region iscritical for VHH folding and solubility because this is the region wherethe light chain would normally be interacting with the heavy chain, andis typically a very hydrophobic region in full-length antibodies.Camelid VHH anitbodies, however, have evolved to accumulate amino acidchanges that make the region more hydrophilic, allowing for the VHH tobe soluble. Interestingly, even though P10 was derived from Llama No: 1,its framework sequences looks more like Llama No: 2's, indicating thatthere were VHH sequences present in Llama No: 1's original library withthe correct framework regions, but biopanning did not favor selection ofthose sequences.

Example 7 Purification of Monovalent and Bivalent VHH

VHH sequences were amplified from T7 phage as monovalent or bivalent(R33 only) VHH and cloned in to pET-47b for expression in E. coli. Thepurified VHH proteins were separated by SDS-PAGE for Coomassie stainingto determine size and purity. All VHH derived from Llama No: 2 werelocated in the soluble fraction after induction, while all of Llama No:1's VHH were located in the pellet, as demonstrated in therepresentative gel in FIG. 13A. This observation is consistent with thesequence analysis that suggested the lack of conserved VHH residues inthe FR2 region of Llama No: 1's sequences might impact solubility.Proteins of approximately 15 kDa for monovalent VHH and approximately 30kDa for bivalent VHH were detected (FIG. 13B).

Example 8 Binding of Monovalent and Bivalent VHH to gD2

The ability of the purified VHH to bind to gD2 was tested by ELISA (FIG.14 14). Surprisingly, despite the high binding of Llama No: 1's VHH togD2 when expressed as a fusion protein on the surface of the phage,purified VHH from Llama No: 1 show minimal binding to gD2. Conversely,while VHH-phage from Llama No: 2 bound poorly to gD2, when expressed andpurified, R33 exhibits superior binding ability. There does not appearto be enhanced binding with bivalent R33 compared to monovalent R33 whenadded in equimolar amounts. It is possible that expression of Llama No:1's VHH as a fusion protein with phage proteins forces the VHH to foldin a way that promotes binding, but when these same VHH sequences areexpressed by E. coli as a monomeric proteins, they are no longerconstrained by flanking phage protein and are unable to fold and bind togD2.

The same pattern of gD2 binding was also demonstrated by flow cytometry.We used FACS analysis with z4/6 cells that express gD2 on their surfaceas a way to measure native gD2 expressed at the cell surface. All VHHderived from Llama No: 2, including the bivalent R33, were again able tobind z4/6 cells, while P4 was unable to bind (FIG. 15).

Example 9 Pentavalent VHH

Based on increasing evidence that VHH have enhanced activity whenexpressed in multivalent context, we expressed R33 as a fusion proteinwith the verotoxin B subunit, which allows for self-assembly into apentamer. The verotoxin B subunit was fused to the N-terminus of R33(NR33) and purified (FIG. 16A). To verify that the NR33 didself-assemble, a sample of the purified NR33 was run through aSuperdex200 column and it was found that they eluted at a peak of about100 kDa, roughly the size of the expected protein (data not shown). Whencorrected for valency, NR33 was able to bind to gD2 as measured by ELISAat similar levels compared to monovalent R33 (FIG. 14B).

Example 10 VHH Neutralization Assay

All forms of the VHH (monovalent, bivalent, pentavalent, were tested inan HSV-2 neutralization assay. R33, bvR33, P4 were unable to neutralizethe virus at the concentrations tested (FIGS. 17A and B). Neutralizationassays with pentameric R33 showed that NR33 does have neutralizingactivity, and that the inhibition compared to untreated virus isstatistically significant at several of the dilutions tested (FIG. 17C).At the highest amount tested (10 μM), NR33 neutralized the virus at 57%and the inhibition remained statistically significant until 0.1 μM.Protein precipitation at higher concentrations prevented testingneutralization activity at higher levels of pentavalent VHH from beingtested, so it is not possible to calculate an IC₅₀ for NR33 from thecompleted experiments, but it is clear from multiple experiments thatthe inhibition is consistent and statistically significant. Furtherprotein purification troubleshooting would likely allow for higherconcentrations to be evaluated.

Example 11 Testing VHH in Vaginal HSV-2 Animal Challenge Model

As shown in Table 1, CF-1 female mice were treated with Depo-provera,and one week after 10 ID₅₀ HSV-2 G was mixed with PBS, P10, R33 andpromptly delivered to the mouse vagina. Three days later the vagina waslavaged, and fluid was plated on foreskin cells to assay for thepresence of virus. At the time of animal testing, the gD2-binding VHHcandidates that were available were R33 and bvR33. P10 was used as thenegative control. Equivalent amounts of R33 and P10 were mixed withvirus and introduced in to the mouse vagina to determine if the VHH hadany HSV-2 in vivo neutralizing capability.

TABLE 1 Testing VHH in Vaginal HSV-2 Animal Challenge Model. SampleInput # Infected Total # % Infected Virus/PBS 10 ID₅₀ 17 24 71% P10 100μM 10 17 59% R33 100 μM 11 18 61%

Example 12 Purified R33ExoA Binds to gD2

Purification of immunotoxins is potentially complicated by the need tooptimize conditions so that the antibody and exotoxin components of themolecule will each fold correctly and maintain their distinct functions.The VHHExoA immunotoxins were purified from induced BL21 cells (FIG.21). Based on protocols published by Buchner et al for an scFvimmunotoxin, the VHHExoA (R33ExoA and P10ExoA) were refolded and theantibody function was tested by ELISA. R33ExoA was still able to bindgD2 at levels comparable to R33 alone, while P10 and P10ExoA had no gD2binding activity (FIG. 19).

Example 13 Purified R33ExoA is Functional as an Immunotoxin

To test the exotoxin capability of the immuntoxin, a MTS assay with z46cells was used that express gD2, and the parental cell line, L cellsthat do not express gD2. Z46 cells are known to not have uniformexpression of gD2, as shown in FIG. 15, through staining with theanti-gD antibody DL6, but levels of gD2 expression should be sufficientto determine if R33ExoA can exert a cytotoxic effect on cells expressinggD2. FIG. 23 demonstrates that R33ExoA only has a cytotoxic effect onz46 cells and not the parental cell line, and that the non-gD2 bindingP10ExoA has no cytotoxic effect on either cell line compared to cellstreated with media alone.

Example 15 Infectious Center Assay (ICA)

To test the cytotoxic effect of the R33ExoA on HSV-2 infected cells, aninfectious center assay was performed (FIG. 21). Cells were infectedwith HSV-2 in the presence of the VHHExoA, and allowed to proceed forroughly 16 hours. Cells were harvested at this time, mixed withuninfected target cells, and then diluted and plated so that the numberof infectious centers can be quantified. R33ExoA consistentlydemonstrated potent antiviral activity compared to P10ExoA and R33 withno ExoA, which had no antiviral activity. Multiple repetitions of theICA revealed that the IC₅₀ of R33ExoA is between 0.01 and 0.1 μM.

Example 16 R33ExoA Activity as a Microbicide

The VHHExoA immunotoxins were tested in the mouse microbicide model todetermine if they have the ability to protect against vaginal HSV-2infection. Three treatments were used: PBS, R33ExoA, and P10ExoA. Theviral inoculum was first mixed with VHHExoA (infection control group wasmixed with PBS) before introduction in to the vagina. At three timepoints post-infection (6, 24, and 48 hours) animals received additionaldoses of VHHExoA proteins (or PBS) so that the immunotoxins were presentin the vagina at times when gD2 would be expressed at the cell surfaceand to mimic the repeated application that would accompany its use as amicrobicide or treatment in humans. As shown in Table 2, the infectioncontrol group (received only PBS) was infected at a frequency of 89% (8out of 9 animals), indicating the virus was properly infectious.Similarly, in the group of animals that received P10ExoA, 7 out of 8, or88% of animals became infected. Only 3 out of 8, or 38%, of animalstreated with R33ExoA became infected, a level that is statisticallysignificant when compared to the infection control group (P=0.048), andapproaches but does not reach statistical significance when compared tothe P10ExoA group (P=0.119). Nonetheless, this result is promising andindicates that further animal testing exploring the use of R33ExoA as amicrobicide or treatment is warranted.

TABLE 2 Testing VHHExoA in Vaginal HSV-2 Animal Challenge Model ViralGroup Input Treatment # Infected Total # % Infected Virus 10 ID₅₀ PBS 89 89% R33ExoA 10 ID₅₀ 10 μM 3 8 38% P10ExoA 10 ID₅₀ 10 μM 7 8 88%(Fisher exact test, two-tailed: Virus Only compared to R33ExoA: p =0.0498; P10ExoA compared to R33ExoA: p = 0.1189)

Example 17

We next sought to examine whether a similar approach might work forHIV-1. Because a broadly neutralizing VHH had already been identified bythe Weiss group (J Exp Med, 2012. 209(6): p. 1091-103), we synthesizedthe DNA encoding the CDR's of that VHH, termed J3, and inserted it intothe VHH backbone DNA from our anti-gD construct, already present in thepET-47b vector. The previously published exotoxin A sequence HA22(Blood, 2004. 103(7): p. 2718-26) with point mutations to removeimmunogenic human B-cell epitopes (Proc Natl Acad Sci USA, 2012.109(29): p. 11782-7) was synthesized and cloned in frame to the Cterminus of the VHH. HA22 encodes a 38-kDa derivative of the 66-kDaPseudomonas exotoxin (PE) in which the cell binding domain of PE (domainIa, amino acids 1-252) and a portion of domain Ib (amino acids 365-380)are deleted. The amino acid sequence of J3VHH with EcoR1 5′ end andAvrll 3′ end is shown in FIG. 23 as SEQ ID NO: 7. The P. aeruginosaExotoxin A subunit which is attached to the 3′ end of SEQ ID NO: 7 inthe full construct, is shown in FIG. 23 as SEQ ID NO: 8. The fullprotein expression sequences with the start codon and His tag andlinkers are shown in FIG. 24 as SEQ ID NOS: X, and Y.

Example 18

We next evaluated the ability of this construct to kill cells expressingHIV-1 envelope. For this purpose 1×10⁴ ENV⁺ and ENV⁻ CHO cells wereincubated with J3ExoA (A), or J3 (B) for 40 h. Cell viability wasdetermined by MTS assay and normalized to 100% for no added protein. Asseen in FIG. 25, only J3ExoA specifically killed envelope expressingcells (p<0.001 for 1, 10 and 100 nM concentrations vs. no treatment),while even at the 100 nM concentration of the J3ExoA the viability ofthe envelope negative cells did not differ significantly from theuntreated controls (p>0.8).

Example 19

Because transformed cells expressing envelope might not berepresentative of expression levels after viral infection, we alsotested the ability of J3ExoA to kill HIV-1 infected primary PBMC fromnormal donors. We first tested the relative neutralizing capability ofJ3 with and without fused ExoA. In this study virus was incubated forone hour with the two VHH constructs, placed on Magi-CCRS cells for onehour and assayed for establishment of infection. As seen in FIG. 26,both constructs retained neutralizing capability, but J3 without ExoAwas clearly more potent (p<0.01 at all concentrations ≧16 nM.

Example 20

We then tested the relative ability of the two constructs to kill HIV-1infected PBMC. For this study PBMC were infected with HIV-1_(BaL) for 24hours and then washed with medium twice and incubated in the presence of50 nM of J3ExoA or J3 for 4 days. Viral persistence was assayed by ELISAof p24 in the culture fluid. IgG was used as the negative control. Theresults (FIG. 27) indicate that despite inferior neutralizing capabilityJ3ExoA significantly reduced p24 levels compared to J3 alone, supportingthe interpretation that, even in the absence of antiretroviral therapy,this VHH is highly effective at killing naturally infected PBMC.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. (canceled)
 2. A heavy chain immunoglobulin of the VHH type orfragment thereof, wherein the heavy chain immunoglobulin of the VHH typeor fragment thereof comprises an amino acid sequence of at least 90%identity to SEQ ID NO: 3 and having affinity for glycoprotein D2 (gD2)of HSV-2 or antigen thereof.
 3. The heavy chain immunoglobulin of theVHH type or fragment thereof of claim 2, wherein the immunoglobulin orfragment thereof is covalently linked to the P. aeruginosa Exotoxin Asubunit.
 4. The heavy chain immunoglobulin of the VHH type or fragmentthereof of claim 3, comprising an amino acid sequence of at least 90%identity to SEQ ID NO:
 4. 5. A multimeric molecule comprising a heavychain immunoglobulin fragment of the VHH type according to claim 4, inwhich VHH sequences are fused to yield multimeric units of 2 or more VHHunits optionally linked via a spacer molecule.
 6. A multimeric moleculecomprising two or more VHH sequences according to claim 4, which arefused to yield 2, 3, 4 or 5 or more VHH units optionally linked via aspacer molecule.
 7. A nucleic acid encoding a heavy chain immunoglobulinfragment of the VHH type according to claim
 2. 8. An expression vectorcomprising the gene encoding the heavy chain immunoglobulin fragmentaccording to claim
 7. 9. The expression vector of claim 8 comprising thenucleic acid sequence of SEQ ID NO:
 4. 10. A micro-organism transformedwith the expression vector of claim
 8. 11. The micro-organism accordingto claim 10, wherein the micro-organism is Lactobacillus.
 12. Themicro-organism according to claim 11, selected from the group consistingof L. jensenii, L. reuteri, L. gasseri, L. crispatus, and L. iners. 13.A method for treatment of an HSV2 infection in as subject, comprisingadministering to the subject, an effective amount of the compositions ofclaim
 2. 14. A method for treatment of an HSV2 infection in as subject,comprising administering to the subject, an effective amount of amicro-organism of claim 12 expressing the heavy chain immunoglobulin orfragment thereof claim
 2. 15. A heavy chain immunoglobulin of the VHHtype or fragment thereof comprising an amino acid sequence of at least85% identity to SEQ ID NO: 7, and having affinity for envelope proteinsof HIV-1.
 16. A heavy chain immunoglobulin of the VHH type or fragmentthereof comprising an amino acid sequence of at least 85% identity toSEQ ID NO: 8, and having affinity for envelope proteins of HIV-1, whichis covalently linked to the P. aeruginosa Exotoxin A subunit.
 17. Theheavy chain immunoglobulin of the VHH type or fragment thereof of claim16, having an amino acid sequence of at least 90% identity to SEQ ID NO:8.
 18. A multimeric molecule comprising a heavy chain immunoglobulinfragment of the VHH type according to claim 16, in which VHH sequencesare fused to yield multimeric units of 2 or more VHH units optionallylinked via a spacer molecule.
 19. A multimeric molecule comprising twoor more VHH sequences according to claim 16, which are fused to yield 2,3, 4 or 5 or more VHH units optionally linked via a spacer molecule. 20.A nucleic acid encoding a heavy chain immunoglobulin fragment of the VHHtype according to claim
 15. 21. An expression vector comprising thenucleic acid encoding a heavy chain immunoglobulin fragment of the VHHtype according to claim
 15. 22. The expression vector of claim 20comprising the nucleic acid sequence of SEQ ID NO:
 6. 23. Amicro-organism transformed with the expression vector of claim
 22. 24. Amicro-organism according to claim 23, wherein the micro-organism isLactobacillus.
 25. The micro-organism according to claim 24, selectedfrom the group consisting of L. jensenii, L. reuteri, L. gasseri, L.crispatus, and L. iners.
 26. A method for treatment of an HIV-1infection in a subject, comprising administering to the subject a heavychain immunoglobulin or fragment thereof of claim
 15. 27. A method fortreatment of an HIV-1 infection in a subject, comprising administeringto subject a micro-organism of claim 23 expressing the heavy chainimmunoglobulin or fragment of claim
 15. 28. A method for treatment of anHSV2 infection in as subject, comprising administering to the subject,an effective amount of a micro-organism of claim 10 expressing the heavychain immunoglobulin or fragment thereof of claim 2, or the multimericmolecule of either of claim 5 or
 6. 29. A method for treatment of anHSV2 infection in a subject, comprising administering to the subject, aneffective amount of the multimeric molecule of claim
 5. 30. A method fortreatment of an HSV2 infection in as subject, comprising administeringto the subject, an effective amount of a micro-organism of claim 12expressing the multimeric molecule of either of claim
 5. 31. A heavychain immunoglobulin of the VHH type or fragment thereof comprising anamino acid sequence of at least 85% identity to SEQ ID NO: 11, andhaving affinity for envelope proteins of HIV-1.
 32. A heavy chainimmunoglobulin of the VHH type or fragment thereof comprising an aminoacid sequence of at least 85% identity to SEQ ID NO: 12, and havingaffinity for envelope proteins of HIV-1, which is covalently linked tothe P. aeruginosa Exotoxin A subunit.
 33. The heavy chain immunoglobulinof the VHH type or fragment thereof of claim 32, having an amino acidsequence of at least 90% identity to SEQ ID NO:
 12. 34. A method fortreatment of an HIV-1 infection in a subject, comprising administeringto the subject the multimeric molecule of claim
 18. 35. A method fortreatment of an HIV-1 infection in a subject, comprising administeringto subject a micro-organism of claim 25 expressing the multimericmolecule of claim
 19. 36. A method for treatment of an HSV2 infection inas subject, comprising administering to the subject, an effective amountof a micro-organism of claim 12 expressing the multimeric molecule ofclaim 6.